Posture-Dependent Corticomotor Excitability Differs Between the Transferred Biceps in Individuals With Tetraplegia and the Biceps of Nonimpaired Individuals.
Carrie L Peterson, Lynn M Rogers, Michael S Bednar and 4 others
PMID 27932695WHAT IT FOUND
The transferred biceps in people with tetraplegia is more electrically excitable at rest in an overhead reach posture than in healthy controls.
This suggests therapists should test which posture works best for each patient rather than assuming a standard position.
Key findings
01Corticomotor excitability of the transferred biceps was significantly greater than in nonimpaired biceps when the arm was in an overhead reach posture.
02Across different individuals, those with higher overall corticomotor excitability generated greater maximum force during elbow extension.
03Within a single person, changing arm posture did not change the relationship between excitability and strength, suggesting biomechanics rather than neural drive dictates force in specific positions.
STILL TO COME
How it was doneWhat they foundWhat it means for PTsWhat it means for OTs
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What it does not show
The study was very small, involving only 5 individuals with tetraplegia. The two weakest arms in the study had poor function before surgery, which may have influenced the results. Measurements were taken at rest; excitability during actual movement might differ. The study design was cross-sectional, so it cannot prove that the posture caused the excitability or that training in this posture will improve function. There was high variability between arms within the same person, meaning results from one side may not apply to the other.
Declared interests
The authors declared no conflicts of interest.
The easy way to misread this
Do not assume that placing every patient in an overhead posture will automatically increase their strength. The study found that while the group average was more excitable in this position, individual variability was high, and strength gains are also limited by biomechanical factors like muscle length.